API Delphi

Question:
When I resize my form, the paint area is clipped, but I need to
repaint the whole area. The form's ClipRect is read only.
How can I get around this?
Answer:
During the resize event, make a call to the Windows API function
InvalidateRect(). Passing nil as the second parameter will cause
the clipping rect of the form to include the entire client area
of the form. The third parameter denotes if the background of
the form should be erased and repainted. Simply calling the
invalidate method of the form may result in a clipping region
and possibly the background getting erased.
Example:
procedure TForm1.FormResize(Sender: TObject);
begin
InvalidateRect(Form1.Handle, nil, false);
end;